We propose that acute lung injury paradigms are likely to be characterized by unique endothelial injury[unreadable] "fingerprints" based on the Ca2+ entry pathways they target and the expression pattern of these channel[unreadable] proteins. Members of the canonical subfamily of transient receptor potential (TRP) proteins comprise[unreadable] subunits of store-operated Ca2+ channels and participate in Ca2+ entry-dependent regulation of lung[unreadable] endothelial permeability in extra-alveolar vessels. Our observation that heart failure leads to loss of the[unreadable] permeability response to store depletion but not that to 14,15-epoxyeicosatrienoic acid (14,15-EET), a lipid[unreadable] that promotes Ca2+ entry-dependent acute lung injury only in alveolar septal capillaries, suggests that 14,15-[unreadable] EET targets a distinct channel expressed in the septal microvasculature. Our preliminary data suggests a[unreadable] novel candidate - TRPV4 - a member of the vanilloid subfamily of TRP proteins. We HYPOTHESIZE that[unreadable] regulation of TRPV4 channels expressed in alveolar septal endothelium integrates the Ca2+ entry-dependent[unreadable] permeability response to diverse stimuli, including heat, EETs, and high vascular pressure. Further, we[unreadable] hypothesize that TRPV4-dependent permeability responses in septal capillary endothelium are independent[unreadable] of store-operated Ca2+ entry pathways, and thus should be retained in chronic heart failure. AIM 1 will[unreadable] determine whether TRPV4 is a common target by which EETs and mechanical perturbation promote Ca2+[unreadable] influx required for increased endothelial permeability in the alveolar septal compartment of the lung, and[unreadable] whether temperature sets the gain of this response. AIM 2 will reveal whether TRPV4-mediated endothelial[unreadable] permeability responses in septal capillaries are retained in chronic heart failure, a model in which storeoperated[unreadable] TRPC channels are down-regulated. We will address these aims using specific measures of[unreadable] permeability and Ca2+ entry in isolated rat and mouse lung, microscopy of lung and vascular corrosion casts[unreadable] to map spatial heterogeneity in the permeability response, pharmacological tools to manipulate signaling[unreadable] pathways implicated in gating of TRPV4, and TRPV4-/- mice. This work will provide the first rigorous[unreadable] analysis of TRPV4 channel expression linked to regulation of endothelial permeability in the intact lung[unreadable] microvasculature.